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<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX This file is generated from xml source: DO NOT EDIT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --><title>Content Negotiation - Apache HTTP Server</title><link href="./style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /><link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /><link href="./style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link href="./images/favicon.ico" rel="shortcut icon" /></head><body id="manual-page"><div id="page-header"><p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p><p class="apache">Apache HTTP Server Version 2.0</p><img alt="" src="./images/feather.gif" /></div><div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div><div id="path"><a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Content Negotiation</h1><div class="toplang"><p><span>Available Languages: </span><a href="./en/content-negotiation.html" title="English"> en </a> |<a href="./ja/content-negotiation.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |<a href="./ko/content-negotiation.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p></div> <p>Apache supports content negotiation as described in the HTTP/1.1 specification. It can choose the best representation of a resource based on the browser-supplied preferences for media type, languages, character set and encoding. It also implements a couple of features to give more intelligent handling of requests from browsers that send incomplete negotiation information.</p> <p>Content negotiation is provided by the <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> module, which is compiled in by default.</p></div><div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#about">About Content Negotiation</a></li><li><img alt="" src="./images/down.gif" /> <a href="#negotiation">Negotiation in Apache</a></li><li><img alt="" src="./images/down.gif" /> <a href="#methods">The Negotiation Methods</a></li><li><img alt="" src="./images/down.gif" /> <a href="#better">Fiddling with Quality Values</a></li><li><img alt="" src="./images/down.gif" /> <a href="#extensions">Extensions to Transparent ContentNegotiation</a></li><li><img alt="" src="./images/down.gif" /> <a href="#naming">Note on hyperlinks and naming conventions</a></li><li><img alt="" src="./images/down.gif" /> <a href="#caching">Note on Caching</a></li><li><img alt="" src="./images/down.gif" /> <a href="#more">More Information</a></li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="about" id="about">About Content Negotiation</a></h2> <p>A resource may be available in several different representations. For example, it might be available in different languages or different media types, or a combination. One way of selecting the most appropriate choice is to give the user an index page, and let them select. However it is often possible for the server to choose automatically. This works because browsers can send, as part of each request, information about what representations they prefer. For example, a browser could indicate that it would like to see information in French, if possible, else English will do. Browsers indicate their preferences by headers in the request. To request only French representations, the browser would send</p><div class="example"><p><code>Accept-Language: fr</code></p></div> <p>Note that this preference will only be applied when there is a choice of representations and they vary by language.</p> <p>As an example of a more complex request, this browser has been configured to accept French and English, but prefer French, and to accept various media types, preferring HTML over plain text or other text types, and preferring GIF or JPEG over other media types, but also allowing any other media type as a last resort:</p><div class="example"><p><code> Accept-Language: fr; q=1.0, en; q=0.5<br /> Accept: text/html; q=1.0, text/*; q=0.8, image/gif; q=0.6, image/jpeg; q=0.6, image/*; q=0.5, */*; q=0.1</code></p></div> <p>Apache supports 'server driven' content negotiation, as defined in the HTTP/1.1 specification. It fully supports the <code>Accept</code>, <code>Accept-Language</code>, <code>Accept-Charset</code> and<code>Accept-Encoding</code> request headers. Apache also supports 'transparent' content negotiation, which is an experimental negotiation protocol defined in RFC 2295 and RFC 2296. It does not offer support for 'feature negotiation' as defined in these RFCs.</p> <p>A <strong>resource</strong> is a conceptual entity identified by a URI (RFC 2396). An HTTP server like Apache provides access to <strong>representations</strong> of the resource(s) within its namespace, with each representation in the form of a sequence of bytes with a defined media type, character set, encoding, etc. Each resource may be associated with zero, one, or more than one representation at any given time. If multiple representations are available, the resource is referred to as <strong>negotiable</strong> and each of its representations is termed a <strong>variant</strong>. The ways in which the variants for a negotiable resource vary are called the <strong>dimensions</strong> of negotiation.</p></div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="negotiation" id="negotiation">Negotiation in Apache</a></h2> <p>In order to negotiate a resource, the server needs to be given information about each of the variants. This is done in one of two ways:</p> <ul> <li>Using a type map (<em>i.e.</em>, a <code>*.var</code> file) which names the files containing the variants explicitly, or</li> <li>Using a 'MultiViews' search, where the server does an implicit filename pattern match and chooses from among the results.</li> </ul> <h3><a name="type-map" id="type-map">Using a type-map file</a></h3> <p>A type map is a document which is associated with the handler named <code>type-map</code> (or, for backwards-compatibility with older Apache configurations, the MIME type <code>application/x-type-map</code>). Note that to use this feature, you must have a handler set in the configuration that defines a file suffix as <code>type-map</code>; this is best done with</p><div class="example"><p><code>AddHandler type-map .var</code></p></div> <p>in the server configuration file.</p> <p>Type map files should have the same name as the resource which they are describing, and have an entry for each available variant; these entries consist of contiguous HTTP-format header lines. Entries for different variants are separated by blank lines. Blank lines are illegal within an entry. It is conventional to begin a map file with an entry for the combined entity as a whole (although this is not required, and if present will be ignored). An example map file is shown below. This file would be named <code>foo.var</code>, as it describes a resource named <code>foo</code>.</p><div class="example"><p><code> URI: foo<br /><br /> URI: foo.en.html<br /> Content-type: text/html<br /> Content-language: en<br /><br /> URI: foo.fr.de.html<br /> Content-type: text/html;charset=iso-8859-2<br /> Content-language: fr, de<br /></code></p></div> <p>Note also that a typemap file will take precedence over the filename's extension, even when Multiviews is on. If the variants have different source qualities, that may be indicated by the "qs" parameter to the media type, as in this picture (available as JPEG, GIF, or ASCII-art): </p><div class="example"><p><code> URI: foo<br /><br /> URI: foo.jpeg<br /> Content-type: image/jpeg; qs=0.8<br /><br /> URI: foo.gif<br /> Content-type: image/gif; qs=0.5<br /><br /> URI: foo.txt<br /> Content-type: text/plain; qs=0.01<br /></code></p></div> <p>qs values can vary in the range 0.000 to 1.000. Note that any variant with a qs value of 0.000 will never be chosen. Variants with no 'qs' parameter value are given a qs factor of 1.0. The qs parameter indicates the relative 'quality' of this variant compared to the other available variants, independent of the client's capabilities. For example, a JPEG file is usually of higher source quality than an ASCII file if it is attempting to represent a photograph. However, if the resource being represented is an original ASCII art, then an ASCII representation would have a higher source quality than a JPEG representation. A qs value is therefore specific to a given variant depending on the nature of the resource it represents.</p> <p>The full list of headers recognized is available in the <a href="mod/mod_negotiation.html#typemaps">mod_negotation typemap</a> documentation.</p><h3><a name="multiviews" id="multiviews">Multiviews</a></h3> <p><code>MultiViews</code> is a per-directory option, meaning it can be set with an <code class="directive"><a href="./mod/core.html#options">Options</a></code> directive within a <code class="directive"><a href="./mod/core.html#directory"><Directory></a></code>, <code class="directive"><a href="./mod/core.html#location"><Location></a></code> or <code class="directive"><a href="./mod/core.html#files"><Files></a></code> section in <code>httpd.conf</code>, or (if <code class="directive"><a href="./mod/core.html#allowoverride">AllowOverride</a></code> is properly set) in <code>.htaccess</code> files. Note that <code>Options All</code> does not set <code>MultiViews</code>; you have to ask for it by name.</p> <p>The effect of <code>MultiViews</code> is as follows: if the server receives a request for <code>/some/dir/foo</code>, if <code>/some/dir</code> has <code>MultiViews</code> enabled, and <code>/some/dir/foo</code> does <em>not</em> exist, then the server reads the directory looking for files named foo.*, and effectively fakes up a type map which names all those files, assigning them the same media types and content-encodings it would have if the client had asked for one of them by name. It then chooses the best match to the client's requirements.</p> <p><code>MultiViews</code> may also apply to searches for the file named by the <code class="directive"><a href="./mod/mod_dir.html#directoryindex">DirectoryIndex</a></code> directive, if the server is trying to index a directory. If the configuration files specify</p><div class="example"><p><code>DirectoryIndex index</code></p></div> <p>then the server will arbitrate between <code>index.html</code> and <code>index.html3</code> if both are present. If neither are present, and <code>index.cgi</code> is there, the server will run it.</p>⌨️ 快捷键说明
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